Partially hydrolyzed aluminum alkyl compounds known as aluminoxanes (a.k.a. alumoxanes) are effective in activating metallocenes for polymerization of olefins. Methylaluminoxane (a.k.a. methylalumoxane) has become the aluminum co-catalyst of choice in the industry. It is available commercially in the form of 10 to 30 wt % solutions in an aromatic solvent, typically toluene.
Modifications to methylaluminoxane have been reported. For example, U.S. Pat. No. 5,329,032 discloses the use of organic groups having electron-rich heteroatoms, such as oxygen or nitrogen, in methylaluminoxane to increase the stability of methylaluminoxane. The organic groups attached to the heteroatom were believed to provide the observed increases in solubility of the methylaluminoxane.
Fluorine species have been reported in aluminoxanes; again, these fluorine species are part of an organic group, which organic group is attached to the aluminum site. See U.S. Pat. No. 6,153,550, where pentafluorophenyl moieties are attached to the aluminoxane, and see U.S. Pat. No. 6,211,111 B1 for additional fluoroaromatic moieties attached to aluminoxanes.
Chlorinated hydrocarbons, particularly dichlorobenzene, have been reported to minimize gel formation when mixed with aluminoxanes. No reaction of the chlorinated hydrocarbons with the aluminoxanes was contemplated or reported; see Japanese Laid-open Patent 49293 (1992).
Halogenated aluminoxanes have been reported in U.S. Pat. No. 6,306,986 B1 (referred to therein as alkylhaloaluminoxanes). These halogenated aluminoxanes are required to have a high degree of halogenation, and are not derived from a pre-made aluminoxane.